Pip install conan like we do on Ubuntu

Author: tkoskela

.github/workflows/cmake.yml

@@ -79,7 +79,8 @@ jobs:
       if: ${{ contains(matrix.os, 'macos') }}
       run: |
         brew update
-        brew install libtiff open-mpi libyaml ccache conan
+        brew install libtiff open-mpi libyaml ccache
+        pip install conan
         echo "CMAKE_PREFIX_PATH=/usr/local/opt/libomp" >> $GITHUB_ENV
 
     - name: Prepare ccache timestamp